Total or partial prosthetic replacements are now common orthopedic surgical procedures. As the age of the general population increases, the number of such replacements is also increasing. Common symptoms generally can be caused by progressive degenerative osteoarthritis, prior localized trauma, previous local surgical procedures within the region, ankylosing spondylitis, and idiopathic skeletal hyperostosis.
A common delayed complication following such replacements is the development of heterotopic ossification within or about the adjacent soft tissue and the prosthesis between the adjoining bone tissue. This complication results from excessive migration, replication, or differentiation of local primitive mesenchymal cells which are stimulated by the surgical trauma. These cells undergo subsequent metabolic and cytologic metamorphosis to become more specialized osteoblastic cells. These osteoblastic cells then produce osteoid which is eventually transformed into calcified deposits or bone tissue, but in undesirable locations.
Heterotopic ossification causes varying degrees of debilitating pain, functional or mobile impairment, and increases the likelihood of repeat procedures after a period of time from several months to a few years. Between 30 and 35 percent of all untreated patients undergoing total hip prosthesis develop some degree of functional impairment or progressive discomfort, often from heterotopic ossification.
It has been shown in our U.S. Pat. No. 6,120,540 that a radio prosthesis comprising a prosthetic device and a radio source material that is part of the prosthesis device has utility, for example, in a total hip replacement. The radio prosthesis is precalibrated to deliver for dosage, dose rate, and depth dose to adjacent target tissue to inhibit growth. Such radiation begins its effective delivery immediately at the time of the procedure and over the immediate critical time frame for heterotopic ossification formation. Since the radiation only travels a short distance to the targeted area, there is minimal exposure of radiation to medical personnel and healthy tissue within the patient. The dosage eventually decays to a non-radioactive state thereby enabling healing without functional impairment to the prosthesis. No separate removal procedure is required. The patient is discharged upon recovery and receives the equivalent radiation benefit of several fractionated external beam treatments without the time, inconvenience, discomfort, and expense of conventional radio therapy.
External beam irradiation has established therapeutic effectiveness. When such therapy is delivered within a narrow period of time, the prophylactic use of external beam radiation therapy has been shown to effectively reduce the incidence and severity of heterotopic ossification. A limited, relatively low-dose of focal ionizing radiation to the specific target tissue, when administered predominantly in the first several hours to two days after surgery has proven beneficial clinical results with virtually no side effects.
Other relevant art includes the following:                U.S. Pat. No. 5,681,289 (Wilcox et al) is a system for dispensing a liquid chemical agent, such as an antibiotic, anesthetic, growth factor, hormone, anti-neoplastic agent into a site of a surgical procedure. The system includes at least one bladder with an internal cavity that connects to an open tube through which the liquid chemical agent is passed, under pressure, into the bladder. The bladder is shaped to fit between a prepared bone section and a prosthesis. The bladder is connected by a tube to a reservoir and pump.        U.S. Pat. No. 4,936,823 (Colvin et al) is an implant capsule for insertion into a body canal of a patient to apply radiation treatment to a selected portion of the body canal. The transendoscopic implant capsule is transported through the body canal to apply a therapeutic radiation to a tumor within the patient. The implant capsule is remotely implanted and retrieved with a fiber optic bronchoscope.        U.S. Pat. No. 5,833,593 (Liprie) is a flexible wire for providing a radioactive source to maneuver through a tortuous narrow passage to a treatment site within the patient. The source wire includes an elongated flexible housing tube with a treatment end modified to receive a radioactive core.        
While U.S. Pat. No. 5,728,136 (Thal) discloses a spike member for insertion into a bone mass, we are unaware of any such device being used to delivery energy treatment to targeted tissue. External beam radiation therapy is often not prescribed because of the time required for set-up and treatment, the availability of single fraction treatments and variations in prescribed dose, patient discomfort and side effects, the need to irradiate tissue outside the target field, and economic considerations. In addition, many patients are not considered for radiation treatment until late in the recovery process, which further limits treatment options.
What is needed is a process and structure for providing the radiation dose originating from an internal site to the targeted tissue, whereby the emission profile more closely matches the profile of the targeted tissue; a process and a structure that can be readily adapted for any surgical bone tissue replacement or additive procedures; a process and a structure that is easy to administer, safe for the patient, effectively reducing side effects caused by such surgical procedures; and, a process and structure for eliminating the need for separate post-operative treatment while dramatically (a) reducing any occurrence of heterotopic ossification, and (b) minimizing infectious processes in tissue within or about the device and excessive, restriction fibroid and scarring at the incision or closure site due to its targeted radiation effects.